The FBI is about to sift through 650,000 emails it found on Anthony Weiner's laptop

US Democratic presidential nominee Hillary Clinton at a campaign rally in Des Moines, Iowa, on Friday. REUTERS/Brian Snyder The FBI will inspect some 650,000 emails found on a laptop belonging to disgraced former congressman Anthony Weiner that may be relevant to an investigation into Hillary Clinton's private email server, The Wall Street Journal reported Sunday night.

The Journal cited sources familiar with the investigation to say that metadata within the messages suggested that thousands could have been sent to or from Clinton's private email server.

The messages were uncovered after investigators seized devices they suspected Weiner, the estranged husband of top Clinton aide Huma Abedin, of using to exchange sexually explicit texts with underage girls.

The investigation into Clinton's private email server was completed in July, with James Comey, the FBI director, recommending that no criminal charges be brought against Clinton for her use of the server while she was secretary of state. But in a vague letter released Friday to congressional leaders, Comey announced the discovery of more emails "that appear to be pertinent" to the Clinton investigation.

The bureau came under fire over the weekend after a Washington Post report revealed that agents had known about the emails since early October but chose not to tell Comey about them until less than two weeks before the presidential election.

Developments over the weekend have laid bare internal strife both within the FBI and between the FBI and the Justice Department in multiple inquiries involving Clinton.

James Comey, the FBI director, at a hearing before the House Oversight and Government Reform Committee on July 7 in Washington, DC. Alex Wong/Getty Images

The Justice Department reportedly asked the FBI not to disclose the discovery of the emails to Congress so close to the November 8 election, but Comey wrote to his employees on Friday that he felt "an obligation to do so given that I testified repeatedly in recent months that our investigation was completed."

Some within the FBI have apparently considered Comey to have overshared various aspects of the Clinton investigation with lawmakers and the public; in July the director gave an unprecedented press conference to announce that the FBI would not recommend criminal charges in the case.

Agents were also frustrated with the FBI leadership's apparent lack of interest in aggressively investigating the Clinton Foundation for possible conflicts of interest and financial crimes, according to The Journal.

The foundation's controversial donation practices came under renewed scrutiny last week when WikiLeaks published a hacked memo titled "Bill Clinton, Inc." that raised questions about the blurring of lines between the charity and the Clintons' personal finances.

Clinton with her husband, former President Bill Clinton, at a rally. AP With no solid evidence of criminal wrongdoing, however, prosecutors within the public-integrity section of the Justice Department — who are not politically appointed — worried that they would be perceived as trying to influence the outcome of the election if they pursued the Clinton Foundation investigation. As such, they reportedly pressured FBI leadership to drop the foundation investigation.

Adding to that perception over the weekend was the revelation that the FBI had not obtained a separate warrant to sift through the roughly 650,000 Clinton emails found on Weiner's laptop before announcing on Friday that the emails existed. Weiner's laptop, which he evidently shared with Abedin, was subpoenaed in late September. The FBI eventually obtained a warrant over the weekend.

Clinton's email scandal has dogged the Democratic presidential nominee for more than a year. She first admitted in March 2015 to exclusively using a private email account to send and receive work-related emails while she served as secretary of state. The controversy compelled her to hand over roughly 30,000 work-related emails to the State Department, which have been released in batches since last year.

But she deleted about 30,000 additional emails from her server that she said were "personal" in nature before handing it over to the FBI in August, five months after she gave individual emails to the State Department.

Donald Trump, who has said he would "lock Clinton up" over her email scandal, seized on the news at a rally Friday. "Clinton's corruption is not on a scale we have ever seen," he told a rowdy crowd. Jonathan Drake/Reuters

Republican presidential nominee Donald Trump, seizing on the issue over the weekend, said during a Sunday rally that the FBI may have renewed the Clinton investigation because it found some of those 30,000 deleted emails. He described them as the potential "mother lode" that could bring down Clinton's candidacy.

Reports have indicated, however, that many of Abedin's emails, going back years, passed through Clinton's inbox at some point and therefore already would have been examined by agents who investigated her server from August 2015 through July of this year.

When asked during a congressional hearing in July whether he would renew the investigation if he "discovered new information that was both relevant and substantial," Comey replied that the FBI "would certainly look at any new and substantial information."